Pressure mat



Oct. 28, 1958 R. HOPKINS PRESSURE MAT Filed J3me 11,

INVENTOR Ruwell Hopkizw ATTORNEYS United States Patent C PRESSURE MATRussell Hopkins, Philadelphia, Pa. Application June ll, 1957, Serial No.665,081

Claims. or. 200-86) This invention relates to pressure mats, andparticularly mats or similar structures responsive to pressure thereonto actuate, a control switch or the like.

At the present time automatic door opening devices are coming into wideuse. Such devices usually consist of a motor of a suitable type arrangedto open or close a door and control means for the motor to start thesame upon approach of a person or vehicle within a predetermineddistance of the door. The present invention relates to a mat structuredesigned to respond to the weight of a person, cart, carriage or thelike to actuate a motor control switch for opening a door or forperforming any other equivalent function. The present invention relatesto structure of the mat, per se, without limitation as to the type ofswitch it actuates or the instrumentality operable in response to switchactuation.

In general, the mat of the present invention comprises a sealed envelopeof resilient material having a metal plate therein overlying a sinuouslyarranged flexible resilient tube. The tube is sealed at one end Withinthe envelope and the other end of the tube extends outwardly of theenvelope and is provided with means for connection to apressure-operated switch or the like. The arrangement is such that theweight of a person, cart or the like on the mat effects compression ofthe air in the tube to such a degree that the pressure is transmitted tothe switch or similar instrumentality. Many arrangements of the mat ofthe present invention with switches or other control devices will beobvious to those skilled in the art.

It is therefore an object of this invention to provide apressure-responsive mat of simple construction, yet highly efficient andsensitive in operation.

It is another object of this invention to provide a pressure mat of thetype described having means for distributing the weight thereon over asubstantial portion of a pressure-responsive conduit therein.

It is still another object of this invention to provide a pressure matstructure capable of being easily and economically fabricated.

Additional objects and advantages will become apparent to those skilledin the art as the description proceeds in connection with theaccompanying drawings, wherein:

Fig. l is a top plan view of a mat constructed in accordance with thepresent invention;

Fig. 2 is an enlarged transverse sectional view through the mat of Fig.1, taken substantially along the line 2-2 of Fig. l; and

Fig. 3 is a perspective view of a portion of the mat of Fig. 1, shown onan enlarged scale and with parts broken away to more clearly illustratethe construction.

The pressure mat of this invention is completely sealed in a resilientenvelope comprising a bottom layer or sheet 2 of suitable material and atop sheet 12. The preferred material for the envelope is neoprene, sincethe latter well-known material has the desired characteristics ofresilience and is yet impervious to air and liquids and is inert to theaction of oils, greases and the like. Overlying Patented Oct. 28, 1958the bottom sheet 2 is a sinuously arranged tube 4 of rubber or neoprene.The tube 4 is, as shown, sinuously arranged with spaced parallelportions closely adjacent each other whereby portions of the conduit ortube 4 are dispersed over substantially the entire area of the mat. .Oneend of the tube 4, as shown at 6 in Fig. 1, is closed and sealed in anysuitable manner. The other end of the tube 4 extends outwardly beyondthe boundaries of the lower sheet 2 andmay be provided with a suitablecoupling 8 for attachment to a control switch or the like. A metal plate10 overlies the sinuously arranged tube 4 and is of substantially thesame'configuration and area as the bottom wall 2 of the envelope. Themetal plate 10 is preferably fairly thin but Ofsuliicient rigidity totransmit or distribute localized pressure to a plurality of adjacentportions of the tube 4 therebeneath.

v()verlying the metal plate 10 is the upper or tread sheet 12, alsopreferably of, neoprene, and the edges of which extend downwardly overthe boundary edges of the plate 10, as at 14, into overlying relation tothe boundary edge portions of the bottom sheet 2. The superposed edgeportions of the sheets 2 and 12 are sealed by means of cement,vulcanization, or in any other suitable manner, throughout theirperipheries to provide a completely sealed envelope enclosing the tubing4 and plate 10.

The tubing 4 is arranged to overlie substantially the entire area of thebottom wall 2 and the terminal runs 16 and 18 are arranged substantiallycoincident with opposed edges of the mat so that they constitutesubstantially the extremities of the mat structure. By arranging theruns 16 and 18 at the extremities of the mat, fairly light pressure suchas would be applied by a light carriage or the like, is first applied inits entirety to the one run of the tube it engages first and with suchconcentration of weight even a light carriage i-s suificient to compressthe air in the tube to the necessary degree to actuate a sensitivecontrol switch connected thereto.

The tubing 4 is preferably of small diameter, for instance, it may beabout inch outside diameter with thin side walls. Such a tubing sealedat one end and connected to a pressure switch at the other end isobviously very susceptible to light pressures applied to the plate 10 tocompress the air trapped in the tubing or conduit to apply pressure tothe switch. Since the tubing is arranged within a sealed envelope, theair trapped in the envelope itself and surrounding the tubing 4 acts asa cushion or-support for the tubing, when heavy pressures are applied,to prevent collapse of one portion of the tubing and expansion ofanother portion without transmitting the necessary pressure through afitting 8 to the switch being controlled thereby. The air trapped in theenvelope gives the mat a firm feeling even though the tubing 4 may havevery thin walls.

Commercially available rubber or neoprene tubing is normallysubstantially straight and when arranged in the sinuous formation shownthen released, the tubing tends to straighten out. It does not remain inthe sinuously arranged configuration unless restrained and held in suchshape. Applicant has found it desirable and advantageous to cement thetubing 4 to either the bottom sheet 2 or to the metal plate 10 or both.A method of assembling the mat disclosed was developed and proved highlysatisfactory. The method consists of first providing the bottom sheet orpanel 2 of the requisite size, then sinuously arranging the rubber tube4 against one face of an adhesive coated metal plate 10. The rubbertubing was thus cemented to the face of the plate 10 and the assemblywas thereupon lifted and manipulated as a unit and brought into thedesired position relative to the bottom sheet 2. Thereafter it was asimple matter to place the upper sheet 12 in position and cement theedge 14 1. In a control mat, superimposed top and bottom walls offlexible material joined at their edges to define a substantially flatenvelope, means defining a flexibly collapsible air conduit in saidenvelope and arranged to have portions thereof dispersed oversubstantially the entire area of said bottom wall, a plate ofsubstantially rigid material inside said envelope and overlying saidconduit means, said conduit means defining a closed and collapsible airchamber in said envelope, and means for connecting a pressure responsivedevice to the otherwise closed interior of said conduit means.

2. A control mat as defined in claim 1 wherein said conduit meanscomprises a sinuously arranged resilient tube having one end sealed andportions thereof extending along and substantially coinciding with atleast one edge extremity of said envelope, the other end thereofextending outwardly of said envelope and constituting said last-namedmeans.

3. A control mat as defined in claim 1 wherein said plate extends oversubstantially the entire area of said mat.

4. A control mat as defined in claim 1 wherein said conduit means is asinuously arranged resilient tube engaging the upper surface of saidbottom wall and the lower surface of said plate, and means adhesivelysecuring said tube to at least one of said surfaces.

5. A control mat as defined in claim 1 wherein said top and bottom wallsare of air impervious material sealed together throughout theirperipheral edges.

References Cited in the file of this patent UNITED STATES PATENTS may 1

